1. Field of the Invention
The present invention relates to an exposure apparatus and a stage device, and a device manufacturing method, and more particularly to an exposure apparatus that is used in a lithographic process when manufacturing electronic devices such as semiconductors and liquid crystal displays and a stage device comprising a stage that moves two dimensionally while holding an object subject to exposure by the exposure apparatus, and a device manufacturing method using the exposure apparatus.
2. Description of the Related Art
At semiconductor manufacturing sites, conventionally, reduction projection exposure apparatus, or the so-called steppers, which use an i-line of a mercury lamp having a wavelength of 365 nm as an illumination light, were used to mass produce circuit devices (such as a 64M(Mega)bit D-RAM) that have a minimum line width of around 0.3 to 0.35 μm. Then, to cope with higher integration of semiconductor devices, exposure apparatus that have a higher resolution have been developed and put to practice. At present, a scanning type exposure apparatus based on a step-and-scan method (referred to as a scanner, or a scanning stepper) that repeatedly performs scanning exposure operations and stepping operations is being widely used. Such a scanning type exposure apparatus uses an ultraviolet pulse laser light having a wavelength of 248 nm from a KrF excimer laser or an ultraviolet pulse laser light having a wavelength of 193 nm from an ArF excimer laser as the illumination light, and by linearly scanning a mask or a reticle on which a circuit pattern is formed (hereinafter generally referred to as a “reticle”) and a wafer serving as a photosensitive object relatively with respect to a projection field of a reduction projection optical system, the exposure apparatus transfers the entire circuit pattern of the reticle onto a shot area on the wafer. With such a scanning stepper, circuit devices which degree of integration are in the 256 Mbit D-RAM class and have a minimum line width of 0.25 μm can be mass produced. Furthermore, exposure apparatus for mass producing circuit devices in the next generation that are 1G(Giga)bit and over are currently being developed.
With the scanning exposure apparatus based on the step-and-scan method, when a pattern of the reticle is sequentially transferred on a plurality of shot areas on the wafer (hereinafter referred to as “shot” as appropriate), in order to improve throughput, the reticle is normally alternately scanned (reciprocally scanned) so as to perform exposure of the following shot. Therefore, when the reticle pattern has been transferred onto a shot, the reticle has to be brought back to the starting position for scanning exposure of the following shot (overscan). In this operation, the reticle is moved further from the point where exposure has been completed by an amount equal to the moving length during prescan (acceleration time to reach a target velocity (scanning velocity during exposure)+settling time of the velocity focusing within a predetermined error range after acceleration is completed) before exposure begins, and corresponding to such an operation, the wafer has to be moved in the scanning direction in addition to the stepping operation for moving the wafer to the next shot (a different shot adjacent to the above shot in the non-scanning direction).
Such stepping operation between shots was conventionally performed in the following procedure, from (1) through (3):    (1) When exposure has been completed, a wafer stage (substrate stage) is temporarily moved to the same coordinate position in the scanning direction as the starting position for scanning exposure of the following shot.    (2) The wafer stage is stepped in the non-scanning direction to the starting position for exposure of the following shot.    (3) The wafer stage begins scanning for exposure of the following shot. Accordingly, the wafer was substantially moved along a path that resembled the letter U. One of the reasons for employing such a path was because in between the above operations (1) and (2), or (2) and (3), or during the above operation (2), control information (including information for setting control parameters) necessary for exposing the following shot was sent from an upper unit to a stage control unit (including a synchronous control unit) that controls the stage. The above control information includes, for example, information related to position control of the reticle stage and wafer stage such as set values of EGA parameters (offsets Ox and Oy of a wafer in an X-direction and a Y-direction, an orthogonality error w of a stage coordinate system that specifies the movement of a wafer, rotation error θ of a wafer, magnification (scaling) errors rx and ry of a wafer in the X and Y directions) obtained by wafer alignment based on an EGA method performed prior to exposure (such values will be data used when setting the position of the wafer on exposure), correction parameter related to the position of both stages during exposure (such as bend information of movable mirrors on the reticle stage side or the wafer stage side), data related to dose control such as data on pulse energy density of the excimer laser and the number of pulse emission, and furthermore, data related to the exposure sequence set. In addition, in some cases the information may include error information of each mechanism while the stage is being moved.
For an exposure apparatus, improving throughput is one of the most important issues, and in order to achieve such a goal, the acceleration-deceleration speed of the reticle as well as the maximum speed during scanning exposure is increasing, as in for example, 0.5 G to 4 G and 350 mm/s to 1500 mm/s, respectively. With this increase, the acceleration-deceleration speed and the maximum speed of the wafer stage during scanning exposure also becomes a value corresponding to the projection magnification. Therefore, the moving length during prescan and overscan required before and after exposure also has to be extended, according to such increase.
Therefore, although the acceleration-deceleration speed and the maximum speed were originally increased from the viewpoint of improving the throughput, there were concerns that the throughput would actually decrease in the long run.
Under such circumstances, requirements for developing a new exposure apparatus that can improve throughput while maintaining other performances of the apparatus are pressing.
Improving the throughput is considered possible, by achieving at least either performing the prescan and overscan operations and the stepping operation of the wafer stage in between shots in parallel, or reducing the moving length of the wafer stage.
However, when the sequence of the above parallel processing or a movement path that reduces the moving length is employed without careful consideration, synchronous accuracy of the reticle stage and wafer stage may decrease and exposure with sufficient accuracy may become difficult, or the time required for synchronous settling of both stages before exposure may increase, or transmitting the control information referred to earlier may prove to be difficult.